In the fats and oils industry, the term “lecithin” is used to refer to a complex mixture of phosphatides that include various classes of compounds based on differences in the polar groups of molecular structures, such as phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylinositol (PI), phosphatic acid (PA) and other substances, such as triglycerides, carbohydrates, etc. In the scientific literature, “lecithin” is often regarded as referring to phosphatidylcholine or PC. The industry use of the term lecithin is applied herein, and the various names for specific phosphatides, such as PC, PE, etc., will be used.
Phosphatidylcholine is used extensively in the pharmaceutical industry, and highly pure PC is quite important for this industry. Recognition of the unique properties and possible uses of individual phosphatide components of lecithin, particularly PC, and the adverse effects in some applications containing contaminating non-choline phosphatides in PC-enriched fractions, have stimulated the search for improved methodologies for PC purification from lecithin.
There are many known methods for obtaining highly-purified phosphatidylcholines from various raw materials. For example, Swiss Pat. No. 561,088 and U.S. Pat. No. 2,945,869 set forth purification processes of soya phosphatidylcholine, which are to be used as emulsifiers for intravenous applications. Alcoholic solutions of previously de-oiled raw phosphatides are treated with Al2O3, MgO and/or activated carbon in order to make these solutions free of cephalins, and especially to reduce, as far as possible, the inositol-containing phosphatides, which have been found to lower the blood pressure in cats when introduced intravenously. However, this procedure always first required removal of the oil from the commercially-available, crude phosphatide prior to the preparation of the alcoholic solutions, which will only lead to a reduction in the cephalin content, regardless of the absorbent being used. The results for such processes demonstrate product purities not exceeding 70%. Accordingly, the complete removal of the cephalin cannot be accomplished by this method.
U.S. Pat. No. 3,544,605 describes a process to obtain highly-purified PC with a high content of essential fatty acids, which is free of, or heavily depleted in, cephalins, from plant lecithin by adsorption of the phosphatides on aluminum oxide and extraction with alcohol. In this process, the crude oil-containing phosphatide is first dissolved in ethyl acetate or a di-chlorinated hydrocarbon having 1 to 4 carbon atoms or a mixture of solvents (without prior de-oiling). The solution is then treated, with stirring, with at least a five-fold amount of aluminum oxide relative to the content of raw phosphatide, or may be carried out by adding the solution to an aluminum oxide column (instead of stirring therewith). Finally, the highly-purified, oil-free PC is liberated with alcohol from the separated aluminum oxide.
German Pat. No. 1,053,299 sets forth a process for obtaining natural choline phosphoric acid diglycerid esters, which are free of colamin, by using an aluminum oxide column chromatography treatment. Here again, an alcoholic extract of the previously de-oiled raw phosphatide, with the prior removal of oil, is achieved by repeated extraction with acetone.
U.S. Pat. No. 4,235,793 describes a process where raw lecithin is first extracted with alcohol. The resulting two phases are separated and the alcohol-rich upper phase is treated with aluminum oxide adsorbent. Elution of the adsorbent with an alcohol leads to an oily phosphatidylcholine, free of cephalin.
U.S. Pat. No. 4,443,378 is related to a method for the separation of acylated phospholipids. This process involves chromatography on a silicic acid gel in a lower alkanol containing 1 to 4 carbon atoms.
Finally, U.S. Pat. No. 4,452,743 is related to a method for the separation of oil and/or phosphatidylethanolamine from alcohol-soluble, phosphatidylcholine products containing the same. This process also involves chromatography on a silicic acid gel in a lower alkanol containing 1 to 4 carbon atoms.
Recently, one of the most important uses of PC involves PC becoming the primary functional ingredient of liposomes, where stable liposomes are formed with high-PC preparations. In order to obtain the best liposomes, 80 to 100% purity PC is required, rendering all of the aforesaid prior art techniques discussed herein inadequate.
Today, column chromatography is considered more appropriate for industrial purification of phosphatides. Chromatographic means are, however, generally slow and costly. On large scales especially, the large quantity of column packing required and the high associated instrumentation costs limit the use of column chromatography to the separation and purification of only the most valuable and expensive compounds. To reduce this cost, many researches have done a great deal of the work, but the results have not been satisfactory.
Therefore, it is an objective of the instant invention to provide more economical approaches and methods for the purification of phosphatidylcholine, and generate purer forms of phosphatidylcholine and like compositions using the aforesaid improved techniques and approaches.
These and many other objects are met in various embodiments of the present invention, offering significant advantages over the known prior art.